Rifle grenade fuze



Feb. 4, 1969 Filed Aug. 21, 1957 R. E. BQWLES RIFLE GRENADE FUZE Sheet 012 INV ENT OR Feb. 4, 1969 E. sowLzs 3,425,349

RIFLE GRENADE FUZE Filed 21. 1957 sheet of 2 F G .3 4a

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3 Claims The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to a rifle grenade fuze, and more particularly to a rifle grenade signature fuze which is adapted to be ballistically armed.

In fuzing of ordnance projectiles, a primary consideration is to maintain a round in a safe and unarmed condition until the round has been properly launched. It has not been feasible in most cases to provide a unique signature of proper launching which cannot be duplicated by conditions which do not completely destroy the round.

Accordingly, a principal object of this invention is to provide an ordnance projectile fuze which recognizes the signature of proper launching in preference to factors that may simulate launching.

Another object is to provide an extremely safe, inexpensive and sturdy rifle grenade fuze.

Still another object is to employ conventional rifle ammunition for launching rifle grenades and arming fuzes contained therein.

An additional object is a rifle grenade fuze system that will be safe and operable after being subjected to accelerations of 100,000 g, be quick acting and permit grenade launching with ball or armor-piercing ammunition.

A further object is a rifle grenade ballistic arming signature fuze that is not detrimental to grenade flight, stability, or dispersion.

Briefly, the foregoing and other objects are attained by rifle grenade ballistic arming systems that feature an assembly of discs and washers which reduces the velocity of a fired round of launching ammunition to a desired value. The launching round first penetrates the assembly and impinges on a plunger secured in a housing. Penetration of the plunger by the launching round results in high forces and pressures that cause the plunger to fail at a selected weakened section and move to a position whereby a plunger-carried detonator moves from a safe position and assumes an effective initiation position adjacent a pyrotechnic booster charge. The fuze is accordingly in an armed position and will enable the grenade to function at grenade impact with a target.

The specific nature of the invention as well as other objects, uses and advantages thereof will clearly appear from the following description and from the accompanying drawing, in which:

FIGURE 1 is a longitudinal sectional view of a portion of a rifle grenade incorporating the fuze of the present invention.

FIGURE 2A is a fragmentary view of the rifle grenade fuze taken substantially along 22 of FIGURE 1 with certain parts removed to illustrate one form of inertia switch contemplated by the present invention.

FIGURE 28 is similar to FIGURE ZA showing deformation of the inertia switch when subjected to a predetermined acceleration.

FIGURE 3 is a partial longitudinal view of a plunger contemplated by this invention.

ited States Patent ice FIGURE 4 is an end view of a modified rifle grenade fuze for use in the rifle grenade illustrated in FIGURE 1.

FIGURE 5 is a longitudinal section taken substantially along 55 of FIGURE 4 with a portion of the plunger shown in full.

FIGURE 6 is an elevation view looking at the device of FIGURE 4 in the direction of the arrow 6 with certain parts broken away.

FIGURE 7 is a longitudinal section taken substantially along 77 of FIGURE 4.

FIGURE 8 is a partial elevation view of FIGURE 7 looking in the direction of the arrow 8.

Referring to FIGURE 1, the partially illustrated rifle grenade comprises a conventional casing 10 containing an explosive charge 12. An elongated tube, generally shown at 14, presents a relatively enlarged cylindrical portion 16 having a cylindrically shaped fuze well 18. The cylindrical fuze well portion 18 may be suitably connected to casing 10 by any one of the many wellknown fabrications substantially as shown.

Tube 14 further comprises another cylindrical portion 20, of somewhat reduced diameter, which is integrally connected to portion 16 and separated therefrom by bulkhead 22. Portion 20 suitably encases a decelerator assembly of washers 24 and discs 26 which may take the form of the bullet decelerator disclosed in application Ser. No. 584,155 filed May 10, 1956, now abandoned, and continuation in part application Ser. No. 731,579, filed Apr. 23, 1958, now US. Patent No. 2,853,008, with a few modifications and reduction in the required number of discs 26 as will become apparent from the description that will follow.

Disposed in fuze well 18 is cylindrical fuze housing 28 that is formed to abut bulkhead 22. Housing 28 has a longitudinal bore 30 at end 32. Bore 30 terminates in a bore 34 of intermediate diameter resulting in shoulder 36. At end 38 of housing 28 a reduced bore 40 of relatively small diameter communicates with bore 34, thus forming shoulder 42.

Adjacent end 38 of housing 28 is substantially cylindrically shaped booster charge 44 which is suitably encased in housing 45 which has an internal bore 46 which may be equal to or slightly larger in diameter than bore 40 of housing 28. The external diameter of booster charge 44 is such that a suitable amount of booster charge 44 is available to insure sympathetic detonation of booster charge 44 when detonator 62 is initiated.

Mounted in housing 28 is plunger 48 which may have cross sections that may be substantially circular. Plunger 48 presents outer annular shoulder 50 that is normally in abutting relationship with shoulder 36 of housing 28. Additionally, plunger 48 has a cylindrical portion 52 having an outer diameter slightly less than the diameter of bore 34 and larger than the diameter of bore 40. A reduced substantially cylindrical portion 54 extends from cylindrical portion 52 as shown and may terminate flush with end 38 of housing 28. Cylindrical portion 54 preferably has its largest external diameter slightly less than that of bore 40 and cooperates with cylindrical portion 52 to form inner annular shoulder 56 that is adapted to abut shoulder 42 of housing 28. An essential part of the invention resides in the provision of a circumferentially disposed weakened portion 58 in plunger 48 located substantially as shown and the purpose of which will become apparent from the description of the operation of the invention that is to follow. A transverse bore 60 is provided in cylindrical portion 54 of plunger 48 to suitably receive a conventional electrical detonator 62 that may be substantially cylindrical in outer configuration.

To retain plunger 48 in housing 28, a buffer 64 is provided that has an elongated bore 66 that extends a major distance therein. Buffer 64 features an annular flange 68 that bears against plunger 48 to maintain outer shoulder 50 of plunger 48 in contact with shoulder 36 of housing 28. A substantially circular sealing washer 70 is advantageously adapted to fit between a cylindrical recessed portion 72 in buffer 64 and the surface of bore 68. To retain Washer 70 in place annular retaining ring 74 may be employed that may also be substantially flush with end 32 of housing 28. It will be noted that buffer 64 may have a cylindrical boss portion 76 that extends through a bore 78 in bulkhead 22 of tube 14 into the disc 26 and washer 24 assembly. Further, housing 28 may be suitably staked at a plurality of locations to retain ring 74 in housing 28.

The fuse electrical firing circuit, in addition to detonator 62, comprises a conventional piezoelectric crystal power supply (not shown) that can be located at the nose of the rifle grenade to generate a sufficient energy potential at grenade impact with a target. The crystal may be connected to ground and through insulated lead 82 to a conductive lug 84 that is coupled to a conductive rivet or eyelet 86. Connected in parallel with the crystal through rivet 86 and ground is a bleeder resistor 88, to reduce the possibility of detonation because of accidental distortion or distortion during grenade flight or distortion due to vibration during grenade flight of the crystal. In series with the crystal is an inertia switch subassembly 90 that may comprise a substantially elliptical thin conductive and resilient band 92 secured to rivet 86 substantially at 94 in any well known manner. A weight 96 is secured to band 92 and under normal conditions the band 92 is designed to remain in contact with a conductive coating 98. Coating 98, which may be silver, is applied to an insulative coating 100, which may be an epoxy resin, which in turn is applied and cured on the entire shoulder 42 and surface 102 of a transverse opening 104 in housing 28. Opening 104 may be employed to aid in mounting and visualizing the inertia switch in housing 28. A transparent plastic window 106 may be provided for sealing opening 104 and also to hermetically support rivet 86. A portion 108 of the side wall of bore 34 may be left intact in forming opening 104 to provide protection for the electrical components disposed in opening 104 at grenade launching as will be apparent shortly.

It will be noted in FIGURES 1 and 3 that cylindrical portion 54 of plunger 48 provided with a reduced diameter cylindrical recess 110 and a longitudinal recess 112 communicating with detonator bore 60 and recess 110.

An epoxy resin insulator coating or layer is applied on the surfaces of portion 108 of the side wall of bore 34 to prevent shorting of the fuze electrical circuit. Similarly, an epoxy resin coating 114, 116, 118, 120, 122, 123 is applied to the remaining side wall surface of bore 34, recess 112, recess 110, cylindrical portion 52, inner shoulder 56, and outer shoulder 50, respectively. A conductive coating or layer 124, 126, 128, and 129, such as silver, is applied over the respective epoxy resin layers on surfaces of recesses 112 and 110, inner shoulder 56, cylindrical portion 52, and outer shoulder 50, respectively. A conductive layer 130 is applied to connect the detonator 62 to conductive coating 124. It will be observed that the fuze electrical circuit is open when plunger 48 is in its initial or first position as shown in FIGURE 1 as a result of conductive layer 126 not contacting layer 98, and that detonator 62 is shorted thru coatings 124, 126, 128, 129, plunger 48 and through the outer casing of detonator 62 Which is in contact with bore 60 of plunger 48. The crystal (not shown) is shorted through resistor 88 as described above.

In another embodiment the effect and functioning of the conductive and insulative coatings or layers is accomplished by providing laminations of conductive and insulative strips.

In operation, the rifle grenade containing the fuzing system of this invention is suitably mounted on a rifle in a manner similar to that shown in patent application Ser. No. 731,579, filed Apr. 23, 1958, now Patent No. 2,853,-

008. A round of launching ammunition is then fired. This round may be in the nature of ball or armor-piercing ammunition. The round of the armor-piercing type first penetrates the stackup of discs 26 and washers 24. After being decelerated to the desired velocity by the stackup, which velocity will depend essentially upon the number, thickness and material of the discs 26, the round penetrates buffer 64. Buffer 64 will have a preset deceleration effect dependent on the material and amount of material penetrated by the round. In penetrating buffer 64, the armorpiercing round will force the side walls of bore 66 to spread radially, thus transmitting a major portion of the forces of the round through the elongated tube 14, and an insignificant amount to the fuze. The round then impinges on the plunger 48 with an ultimate desirable velocity. Penetrating the plunger 48 to be ultimately embedded therein, the round will produce relatively large forces and pressures on the plunger 48, causing the plunger 48 to fail in tension at weakened section 58. Plunger 48 will then advance until inner shoulder 56 of plunger 48 abuts shoulder 42 of housing 28. At this final or second position of plunger 48, detonator 62 Will be proximate booster charge 44, and thus in an effective position to initiate grenade detonation. At the second position of plunger 48, it will be noted that conductive layer 126 on outer shoulder 56 is in contact with conductive layer 98 on shoulder 42. Consequently, the fuze electrical circuit is closed. Further observation of FIGURES 1 to 3 will reveal that the electrically conductive paths are clearly defined and the possibility of undesirable short circuiting is remote.

As the rifle grenade of FIGURE 1 is launched and for a period thereafter the usual setback forces will be present. These setback forces will act upon inertia switch resulting in weight 96 causing resilient band 92 to disengage from conductive layer 98 as illustrated in FIGURE 2B. It will be noted that the band 92 flattens to engage the side walls of opening 104 in housing 28, thus grounding out the crystal during setback. Accordingly, the fuze circuit is open and accidental or undesirable detonation is insured against at launching. When the setback forces cease, band 92 will once again engage conductive strip 98.

At grenade impact with a target suflicient energy will be generated as a result of the distortion of the piezoelectric crystal to cause detonation of the rifle grenade. Additionally, at grenade impact firm contact of conductive layer 126 and 98 is further insured as a result of the inertia forces developed to obviate any possibility of fuze malfunction.

With proper design of the weakened section 58, which can be readily varied to give :any predetermined failure or response, the fuze of FIGURE 1 will remain safe and operable when subjected to accelerations of over 100,000 g. It will be obvious that the plunger 48 and housing 28 may be modified so that a weakened section will fail by compression or shear forces developed by the fired round of ammunition. In addition, another embodiment of this invention may feature a battery and contact-type initiator subassembly in replacement of the piezoelectric crystal power supply.

If ball ammunition is used, a lesser number of discs 26 are essential to produce a suitable deceleration of the ball ammunition round. The last disc 26 to fail in shear will abut against buffer 64. Sufficient energy will be remaining because of the traveling ball ammunition round to cause the buffer 64 to fail at weakened section 69. Buffer 64 will then he possessed of enough energy to enable plunger 48 to fail at weakened section 58. The remaining fuze operations are the same as that described above.

It will be noted that flange 68, washer 70, ring 74 and flange 59 serve the additional purpose of transmitting forces and pressures so that no undue or undesirable strains and stresses are placed on weakened sections 58 and 69, resulting from accidental or undesirable projectile movements.

Another embodiment of the present invention is illustrated in FIGURES 48. A housing 228 is provided with bore 230 at end 232 thereof. Bore 230 communicates with a lesser diameter bore 234 to form shoulder 236 at end 238 of housing 228. Bore 240 communicates with bore 234 to form shoulder 242.

In housing 228 is plunger 48 which may be the same as the plunger 48 of the embodiment of FIGURES 1-3. Accordingly, for a description of this plunger and the associated detonator and coatings reference should be made to the description of FIGURES 1-3 since like numerals will be employed to designate substantially like parts.

A butter 64, washer 70, and ring 72 may be provided in this embodiment substantially in the same manner as in FIGURES 1-3. Thus, reference to the latter embodiment should be made for a description of these parts. Housing 228 may be suitably staked at a plurality of points to maintain washer 74 in bore 230.

The fuze firing circuit may comprise a thermal battery power supply 282 the structural components of which are Well known to those skilled in the art. As shown in FIG- URE 7, housing 228, and if necessary plunger 48 and buffer 64 together with washer 70 may be suitably recessed generally at 284, 286, 288 respectively, to conveniently receive the thermal battery 282. The usual battery firing pin 290 may be supported on a Teflon bushing 292 which is suitably mounted on buffer 264. Battery 282 preferably reaches a working voltage of approximately between 0.1 and 0.2 second after initiation, to provide a safe arming distance. Further battery 282 should maintain a working voltage for at least twelve seconds after activation and provide sufiicient energy for reliable detonator operation during one millisecond of a closed fuzing circuit condition. It is also desirable that the battery 282 be hermetically sealed in housing 228. Battery 282 is suitably connected to ground and has, distal firing pin 290, terminal 294 in contact with one end of a conducting strip 296 that is suitably insulated from housing 228 as at 297. The other end of strip 296 is suitably coupled with a trembler switch assembly 298 which forms the subject matter of application Ser. No. 675,233 to I-Ierman R. Kollmeyer, filed July 30, 1957. In general, the switch assembly 298 is normally open and remains open during launching and free flight. The switch assembly 298 also provides a closed contact time of at least 150 microseconds for accelerations greater than 50 g that may be directed from the forward hemisphere of a sphere that may envelope the switch. Further the switch assembly 298 is adapted to close within one millisecond at 500 g acceleration which approximately corresponds to the static crushing resistance of some presently used rifle grenades. Switch assembly 298 is adapted to be conveniently fitted into a recessed portion 300 at the outer periphery of housing 228 and be suitably secured therein.

An insulative coating or layer such as an epoxy resin is applied to shoulder 242, the side wall surface of bore 234 and shoulder 236. A conductive coating or layer 302, such as silver, is applied over the resin on shoulder 242. Coating 302 is advantageously coupled with lead 304 extending from switch assembly 298.

The arming of this embodiment is substantially the same as that of FIGURES 1-3. Generally the detonator 62 will be fired at grenade impact by the energy supplied from battery 282 which is activated at grenade launching since the switch assembly 298 will close at impact the normally opened fuzing circuit. In conclusion it will be observed that this embodiment has the distinct advantage of being a self contained and complete fuze system that is base-located and base-initiated.

It will be apparent that the embodiments shown are only exemplary and that various modifications can be made in construction and arrangement within the scope of the invention as defined in the appended claims.

I claim:

1. An improved rifle grenade, said grenade comprising: a tube; a cylindrical fuze well having an open end and a bottom in one end of said tube; bullet decelerating means in the opposite end of said tube; a housing in said fuze well, said housing having one end in contact with the bottom of said fuze well; an explosive in contact with the other end of said housing opposite said one end thereof; a cavity in said explosive; an inwardly projecting shoulder in said other end of said housing; a first electrically conducting coating on the housing shoulder; switch means electrically connected to said first conductive coating; an opening in said other end of said container communicating with said cavity; a plunger having first and second ends in said housing, said first end positioned in said opening and constructed and arranged for insertion into said cavity; a detonator mounted in said first end, the second end of said plunger positioned adjacent said bullet decelerating means; inner and outer shoulders on said plunger intermediate said first and second ends thereof; a frangible section connecting said inner and outer shoulders; said section constructed so as to break upon receiving a bullet-produced impact of some predetermined magnitude; a second electrically conductive coating on said shoulders; an electrical connection between said detonator and said second conductive coating, said outer shoulder retaining said plunger in the housing opening with the inner shoulder and said second conductive coating spaced from said first conductive coating, said second coating and said inner shoulder positioned to abut said first coating and said housing shoulder, said bullet deceleration means being positioned to drive said tube when penetrated by a bullet and constructed so as to allow said bullet to pass therethrough and impact against said second end of said plunger, thereby breaking said frangible section and driving said detonator into said cavity, said inner shoulder and said second conductive coating abutting said housing shoulder and said first conductive coating, said switch thereupon initiating detonation of said detonator by means of abutting conductive coatings.

2. An improved rifle grenade comprising: a tube; a cylindrical fuze well and bullet decelerating means mounted in opposite ends of said tube, said bullet decelerating means comprising a stack of fiat disks and washers, said disks having a thickness sufficient to decelerate a bullet fired therethrough to some predetermined velocity, said washers interposed between said disks to guide a bullet through said disks; an explosive charge in said tube contacting said fuze Well; a cavity in said explosive charge; a plunger having first and second ends in said fuze well, the first end of said plunger positioned for movement into said cavity; a detonator mounted in said first end of said plunger, the second end of said plunger positioned adjacent said bullet decelerating means; inner and outer circumferential shoulders extending from said plunger intermediate the ends thereof, said outer shoulder being fixedly mounted in said fuze well retaining said plunger against movement therein; a frangible section connecting said inner and outer shoulders and constructed so as to break upon receiving a bullet impact of some predetermined magnitude; said bullet decelerating means driving said tube when a bullet is fired therethrough, said bullet penetrating said disks with a magnitude suflicient to break said frangible section thereby driving said detonator into said cavity, said detonator adapted -to be detonated in said cavity.

3. An improved rifle grenade comprising: a tube; a fuze Well and bullet decelerating means mounted in opposite ends of said tube; said bullet decelerating means comprising a stack of flat disks arranged substantially perpendicular to the line of bullet movement, said stack of disks decelerating a bullet fired therethrough to some predetermined velocity; an explosive charge in said tube contacting said fuze well; a cavity in said explosive charge;

a plunger having first and second ends in said fuze Well, the first end of said plunger positioned for movement into said cavity; a detonator mounted in said first end of said plunger, the second end of said plunger positioned adjacent said bullet decelerating means; inner and outer circumferential shoulders extending from said plunger intermediate the ends thereof, said outer shoulder being fixedly mounted in said fuze Well retaining said plunger against movement therein; a frangible section connecting said inner and outer shoulders and constructed so as to break upon receiving a bullet impact of some predetermined magnitude; said bullet decelerating means driving said tube when a bullet is fired therethrough, said bullet penetrating said disks with a magnitude sufiicient to break said frangible section thereby driving said detonator into said cavity, said detonator adapted to be detonated While in said cavity.

References Cited UNITED STATES PATENTS FOREIGN PATENTS Great Britain.

VERLIN R. PENDEGRASS, Primary Examiner.

US. Cl. X.R. 

1. AN IMPROVED RIFLE GRENADE, SAID GRENADE COMPRISING A TUBE; A CYLINDRICAL FUZE WELL HAVING AN OPEN END AND A BOTTOM IN ONE END OF SAID TUBE; BULLET DECELERATING MEANS IN THE OPPOSITE END OF SAID TUBE; A HOUSING IN SAID FUZE WELL, SAID HOUSING HAVING ONE END IN CONTACT WITH THE BOTTOM OF SAID FUZE WELL; AN EXPLOSIVE IN CONTACT WITH THE OTHER END OF SAID HOUSING OPPOSITE SAID ONE END THEREOF; A CAVITY IN SAID EXPLOSIVE; AN INWARDLY PROJECTING SHOULDER IN SAID OTHER END OF SAID HOUSING; A FIRST ELECTRICALLY CONDUCTING COATING ON THE HOUSING SHOULDER; SWITCH MEANS ELECTRICALLY CONNECTED TO SAID FIRST CONDUCTIVE COATING; AN OPENING IN SAID OTHER END OF SAID CONTAINER COMMUNICATING WITH SAID CAVITY; A PLUNGER HAVING FIRST AND SECOND ENDS IN SAID HOUSING, SAID FIRST END POSITIONED IN SAID OPENING AND CONSTRUCTED AND ARRANGED FOR INSERTION INTO SAID CAVITY; A DETONATOR MOUNTED IN SAID FIRST END, THE SECOND END OF SAID PLUNGER POSITIONED ADJACENT SAID BULLET DECELERATING MEANS; INNER AND OUTER SHOULDERS ON SAID PLUNGER INTERMEDIATE SAID FIRST AND SECOND ENDS THEREOF; A FRANGIBLE SECTION CONNECTING SAID INNER AND OUTER SHOULDERS; SAID SECTION CONSTRUCTED SO AS TO BREAK UPON RECEIVING A BULLET-PRODUCED IMPACT OF SOME PREDETERMINED MAGNITUDE; A SECOND ELECTRICALLY CONDUCTIVE COATING ON SAID SHOULDERS; AND ELECTRICAL CONNECTION BETWEEN SAID DETONATOR AND SAID SECOND CONDUCTIVE COATING, SAID OUTER SHOULDER RETAINING SAID PLUNGER IN THE HOUSING OPENING WITH THE INNER SHOULDER AND SAID SECOND CONDUCTIVE COATING SPACED FROM SAID FIRST CONDUCTIVE COATING, SAID SECOND COATING AND SAID INNER SHOULDER POSITIONED TO ABUT SAID FIRST COATING AND SAID HOUSING SHOULDER, SAID BULLET DECELERATION MEANS BEING POSITIONED TO DRIVE SAID TUBE WHEN PENETRATED BY A BULLET AND CONSTRUCTED SO AS TO ALLOW SAID BULLET TO PASS THERETHROUGH AND IMPACT AGAINST SAID SECOND END OF SAID PLUNGER, THEREBY BREAKING SAID FRANGIBLE SECTION AND DRIVING SAID DETONATOR INTO SAID CAVITY, SAID INNER SHOULDER AND SAID SECOND CONDUCTIVE COATING ABUTTING SAID HOUSING SHOULDER AND SAID FIRST CONDUCTIVE COATING, SAID SWITCH THEREUPON INITIATING DETONATION OF SAID DETONATOR BY MEANS OF ABUTTING CONDUCTIVE COATINGS. 